USS Kearsarge: Replenishment at sea time lapse

The Kearsarge (an assault ship) hooks up with a supply ship. They need to do this while underway to maintain steerage. In laymen’s terms, ships can’t steer if they aren’t moving, and if they stayed still they would smash into each other. (Staying still isn’t tactically advantageous either.) This is similar to aerial refueling by jets.